Control Flow & Conditionals in C++ (`if`, `else`, `switch`)

🟢 Beginner

📖 Definition

Conditional Statements allow a program to make decision choices and execute specific blocks of code depending on whether boolean conditions evaluate to true or false. C++ provides if, else if, else, and switch statements for control flow branch selection.

🇮🇳 Hindi Explanation

Conditionals ka matlab hai code ko shart (condition) ke hisaab se chalana.

if tab chalta hai jab condition true ho.
else if tab chalta hai jab pehli if condition false ho aur nayi condition check karni ho.
else tab chalta hai jab saari conditions false ho jayein.
switch ek hi variable ki alag-alag exact values (case 1, case 2) ko fast match karne ke liye use hota hai.

🚩 Marathi Explanation

Conditionals cha vapar karun aapan conditions var aadharit code run karto.

if: Condition true aslyas chalte.
else if: Pahili condition false aslyas dusri condition tapasnyasathi.
else: Sarva conditions false aslyas.
switch: Eka variable chya nirdharit values (case) tapasnyasathi.

📝 Syntax & Branching Structure

1. `if - else if - else` Ladder

if (condition1) {
    // Code executed if condition1 is true
} else if (condition2) {
    // Code executed if condition2 is true
} else {
    // Code executed if all conditions are false
}

2. `switch - case` Statement

switch (expression) {
    case value1:
        // Statements
        break; // Prevents fall-through!
    case value2:
        // Statements
        break;
    default:
        // Fallback statements
        break;
}

💡 Practical Example

#include <iostream>

int main() {
    int score = 85;
    char grade;

    std::cout << "=== GRADE EVALUATION SYSTEM ===" << std::endl;

    // 1. if - else if - else Ladder
    if (score >= 90) {
        grade = 'A';
    } else if (score >= 80) {
        grade = 'B';
    } else if (score >= 70) {
        grade = 'C';
    } else if (score >= 60) {
        grade = 'D';
    } else {
        grade = 'F';
    }

    std::cout << "Score: " << score << " | Assigned Grade: " << grade << std::endl;

    // 2. switch - case Statement
    std::cout << "\n--- GRADE REMARKS ---" << std::endl;
    switch (grade) {
        case 'A':
            std::cout << "Remark: Outstanding Performance!" << std::endl;
            break;
        case 'B':
            std::cout << "Remark: Excellent Job!" << std::endl;
            break;
        case 'C':
            std::cout << "Remark: Good Effort!" << std::endl;
            break;
        case 'D':
            std::cout << "Remark: Needs Improvement." << std::endl;
            break;
        case 'F':
            std::cout << "Remark: Failed. Please retake the test." << std::endl;
            break;
        default:
            std::cout << "Invalid Grade." << std::endl;
            break;
    }

    return 0;
}

🔍 Code Breakdown

if (score >= 90): Evaluates first. Since 85 >= 90 is false, execution moves to the next branch else if (score >= 80).
score >= 80: Evaluates to true, assigning 'B' to grade. Subsequent else if branches are skipped.
break inside switch: Immediately exits the switch block. Without break, execution continues sequentially into the next case (known as fall-through).

👀 Output

=== GRADE EVALUATION SYSTEM ===
Score: 85 | Assigned Grade: B

--- GRADE REMARKS ---
Remark: Excellent Job!

⚠️ Common Mistakes

Forgetting break in switch Cases: Omitting break causes C++ to execute subsequent case statements even if their values do not match!
Using switch with Floating Point Numbers or Strings: Standard C++ switch works strictly on integral types (int, char, enum). You cannot write switch(double_val) or switch(string_val). Use if-else for strings and doubles.

🛡️ Best Practices

Always include a default: label in switch statements to handle unexpected or fallback values cleanly.

🧪 Try It Yourself

Input an integer from the user and check whether it is Positive, Negative, or Zero.
Input a year and check if it is a Leap Year ((year % 4 == 0 && year % 100 != 0) || (year % 400 == 0)).

🎯 Mini Challenge

Write a mini calculator using a switch statement that inputs 2 numbers and an operator character (+, -, *, /) and prints the result.

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Control Flow & Conditionals in C++ (if, else, switch)